Method of manufacturing encapsulated electrical units



Sept. 8, 1964 R. L- WHEARLEY 3,147,540

METHOD OF MANUFACTURING ENCAPSULATED ELECTRICAL UNITS Original Filed May23, 1957 5 Sheets-Sheet 1 INVENTOR. ROBERT L. WHEARLEY ATTORNEYS Sept.8, 1964 R- 1.. WHEARLEY 3,1475540 METHOD OF MANUFACTURING ENCAPSULATEDELECTRICAL UNITS Original Filed May 23, 1957 5 Sheets-Sheet 2 INVENTOR.ROBERT L. WHEARLEY Sept. 8, 1964 WHEARLEY METHOD OF MANUFACTURINGENCAPSULATED ELECTRICAL UNITS Original Filed May 23, 1957 5 Sheets-Sheet3 22 :imm K6 K3 V- 1 E L 1 1 R 1 1 1/ 1 1 1 11 1 111 1 R A 1 1 1 1 1 1 11 1 1 1 0 I I l I I m w 1 IL 1 1 1 1 1 1 1 1 1 1 1 1 1 T 1 1 1 1 1 1 1 11 1 R E B o R w H 11 FIG-9 ATTORNEYS United States Patent This inventionrelates to encapsulated electrical components and particularly, tomethods of manufacture thereof and is a division of my pendingapplication, Serial No. 661,169, filed May 23, 1957, entitled ElectricalApparatus and Method of Manufacturing the Same, now Patent No.2,982,888.

It is of importance with many electrical devices such as solenoids,resistors and armature receiving coils that the wire component be sealedboth in order that constant electrical values may be maintained and thedevice be protected against the actions of moisture, vapors, and heat,for example.

A primary object of this invention is to provide an improved methodmaking encapsulated components in which the encapsulating material maybe either organic or inorganic.

A principal object of this invention is to provide novel methods ofconstructing encapsulated electrical components which the methods permitthe usage of either inorganic or organic insulating materials.

A particular feature of the invention resides in the provision of amethod of making encapsulated electrical components which are resistantto high temperatures, that is 400-500 C. This is accomplished in thepractice of the invention by utilizing inorganic electrical insulatingmaterials of relatively high softening point.

In the preferred embodiment of the invention the encapsulated componentis produced by winding wire into grooves of a sleeve, for example, thesleeve being 0onstituted of electrical insulating material; over thefirst wound sleeve is placed a second sleeve in concentric relaslu'pwith the first, and this second sleeve is likewise wound with wire tothus form a pair of windings in spaced insulated relation. The windingsare so formed as to be connected in electrical series, and the turns ofthe wire are insulated from each other. As many such windings as isdesired may be formed on concentrically disposed sleeves and thereafterthe assembly operation is completed by the provision of a coveringsleeve of ungrooved insulating material. The assembly is then supportedin a mold body and heated sufficiently to cause the insulating materialto assume a viscous, flowable state and the insulating material enclosesand securely fixes the windings while sealing the assembly. Cooling andremoval from the mold body provide a completed encapsulated unit.

The procedure lends itself to mass production methods both in assemblyand sealing as will be noted from the detailed description set outhereinafter.

The invention will be more fully understood by reference to thefollowing detailed description and accompanying drawings wherein:

FIGURE 1 is a view of coil form used in the practice coil form which isadapted to be slid over the wound coil form of FIGURE 3;

FIGURE 6 illustrates the coil form of FIGURE 5 in position and beingwound;

FIGURE 7 illustrates an electrical component wound and ready to beplaced in a mold body;

FIGURE 8 illustrates the structure of FIGURE 7 within a mold body;

FIGURE 9 is a fragmentary view of the structure of FIGURE 8 illustratinga mold end plate arrangement;

FIGURE 10 is a perspective View of an encapsulated component;

FIGURE 11 is a view partially in section of a further embodiment of thestructure of invention; and

FIGURE 12 is a sectional view of yet another embodiment of theinvention.

In the practice of the invention the insulating material which supportsand spaces the windings may as already noted be inorganic or organic.Thus siliceous materials such as glass and polymerizable plastics areemployable. The invention will be described in specific relation tosiliceous materials however as such afford a generally higher anddesirable heat resistance.

Referring to the drawing the numeral 1 designates a sleeve of glasshaving an axial bore 2, and grooves 3 forming a spiral over the sleevelength. Rightwardly (FIGURE 1) the sleeve has an axial extending passage4. As shown in FIGURE 3 the bore 2 receives a removable core 6preferably of a metal of high melting point-and the sleeve is supportedthereby for rotation on shafts 7, 8 which may respectively be associatedwith a head-stock and tail-stock of a lathe, for example.

Electrically conductive wire 9 is drawn from a suitable source (notshown) and applied by traverse mechanism indicated generally at 10 tothe sleeve 1 as shown (FIGURES 3 and 4). The first end of the wireindicated at 11 extends through passage 4 and serves as a holding meansin the winding operation; also wire end 11 functions as a lead in theend product. The grooves and wire diameter are so related that the wirelies in the grooves and does not protrude above the sleeve surface.

Each sleeve of the component may be wound separately and the windingsthen connected in series electrically by splicing the wires. Howeverwith the arrangement shown in FIGURES 3, 4 and 5 continuous winding maybe effected. As shown in FIGURE 5 sleeve 12 has an axial bore 13,grooves 14 and is slotted through longitudinally at 15. Sleeve 12 asshown in the illustration also has a passage corresponding to thepassage 4 of sleeve 1; where however more than 2 sleeves are employedthe passages would normally appear only in the sleeve supporting theinner and outer windings and the remaining sleeves would be slottedthrough at both ends as at 15. Slot 15 is for the purpose for passingthe wire continuously from the lower sleeve to the upper for windingformation on the upper sleeve.

The shaft 7 may be driven in either direction of rotation andaccordingly the wire passing through slot 15 may be spiraled on theouter sleeve in a direction of the coil turns such that the turns aredirectly over those of the first sleeve or such that the turns are in anopposite direction to those of the first sleeve. By bringing wire 9through slot 15 and maintaining the same direction of sleeve rotation aswith the first sleeve the windings are in criss-cross relation on thetwo sleeves. With most wires the flexibility is such that the wireconforms readily to the sleeve contour; however if desired a drop ofglaze on the wire at slot 15 will hold the wire appropriately positionedfor winding in the left to right direction (FIG- URE 6).

Alternatively, to secure a desired winding arrangement for a particularapplication the wound sleeve may be demounted and turned end to endbefore receiving the second sleeve which latter sleeve may have asufiicient length of axial slot as 15 to conveniently receive the wireand to pass the wound first sleeve.

The second sleeve 12 fits the first sleeve closely and may itselfreceive other Wound sleeves thereon. As shown in FIGURE 7 however sleeve12 receives a sleeve 17 of glass having no grooves and this sleeveserves as a covering sleeve.

The assembly of FIGURE 7 including the metal core 6 as shown in FIGURE 8is slid into a mold body which comprises end plate 18; a tube 19 weldedto plate 18 and adapted to receive the assembly in sliding engagement asshown; end plate 23; and threaded rods 21 which pass through the endplates and receive nuts 22 to securely retain the assembly on the moldbody between the plates. Suitably end plate 23 is recessed at 23 toreceive the wire ends or the ends may be passed out through plate 23.

The assembly, confined within the mold, is then placed within an ovenand heated to a temperature suflicient to render the siliceous materialor glass material of the sleeves at least viscous enough to flow aboutthe conductor wires. Suitably for mass production a tunnel is providedand the assemblies within the mold bodies are passed through the tunnelon a conveyor.

Upon removal from the heat the assembly is cooled to about roomtemperature the mold removed and the core 6 taken from the assembly. Theproduct will then appear as generally designated at 24 in FIGURE and isa compact arrangement of windings in sleeved relationship insulated bythe siliceous material peripherally and endwise but connected togetherin electrical series.

Glasses suitable for the product of invention may have softening pointsas low as 900 F. and preferably have thermal coefficients of expansionclosely approaching that of the electrically conductive wire. Siliceousmaterials embodying relatively high percentages of lead oxide, boricoxide and alumina are useful as low softening point glasses; appropriateproportioning of such materials permits the attainment of substantiallyany desired thermal coefficient of expansion.

Borosilicates are also suitable, particularly the soft borosilicateshaving softening points of 1600 F.1800 F.; the silica-lime-aluminasystem glasses may also be employed.

It is not necessary that a single electrically insulating material beemployed. For example a low softening point glass may be utilized for anintermediate sleeve as 12 in FIGURE 8. The temperature then need only beraised to the softening point of this material to secure a complete sealfor sleeve 12 when it becomes viscous will adhere to the wire of thewindings and the solid sleeves 1 and 17. Care should be taken to inhibitflow to the recess 23 and for this reason it is desirable to heat theassembly with plate 23 uppermost. Any glass adhering to leads 11, 16 maybe readily scraped therefrom. A combination of a lead glass and a softborosilicate or a hard borosilicate may be thus employed, theborosilicates forming the inner and outer sleeves. Also other highsoftening point electrical insulating materials, the ceramics forexample, may be employed in such a composite.

An embodiment having a greater plurality of concentric windings is shownin FIGURE 11. The product is constructed as described hereinbefore butcomprises a winding on inner sleeve 25 of high softening point glass, anouter sleeve 26 also of relatively high softening point glass, andintermediate sleeves 27, 28, 29 each having windings thereon. Suitablysleeve 28 is also of high softening point glass while the sleeves 27, 29are of low softening point material. Raising the temperature to anextent sufficient-that is 900 F. to 1300 F. to soften the material ofsleeves 27, 29 is effective to enclose and l seal the windings. Underthis condition the high softening point materials such as theborosilicates remain solid during the heating and the turns of wireremain securely fixed during the heating.

Leads 11, 16 of the structure of FIGURE ll extend from one end only ofthe component since the device is wound as described in connection withFIGURE 3 and has an even number of windings.

In the embodiment of FIGURE 12 the windings are an odd number and theleads 32, 33 extend from opposite ends. The sleeves with the windingsthereon are designated by the numerals 34, 35, 36 and the outer sleeveis indicated at 37. The sleeves may be all of one softening point or theintermediate sleeve 35 may be of a different softening point than thebounding sleeves 34, 36. In this instance the component has a solid coreof insulating material 39 and is suitable as a resistor. The glass 39may be integral with the glass 34; or the glass 39 may be a low fusionpoint material deposited in the core hole after complete formation ofthe component and fused in place.

As already noted it is preferable that the encasing insulating materialand the wire of the windings have approximately the same coefficients ofthermal expansion. Such is desirable where the windings are to beoperated under high temperature conditions in order to avoid strains inthe encasing material. Suitable materials for the wire include copper,steel, nickel, silver, aluminum, aluminum coated silver, and coppercoated alloys such as the nickel-iron alloys; a nickel-iron alloycontaining about 48% by weight of nickel and 52% by weight of iron,copper clad if so desired is useful. No insulation coating is requiredon the wire itself in the practice of the invention; bare wire isemployed but insulation may be employed as a coating where temperatureand operating conditions permit.

The wire diameters useful range from the very fine to the large sizes ofmagnet wire for example from #50 American wire gauge (about .001) to #10(about 0.1). The bare wire may be wound as closely as the spacing of thegrooves permit. While for the sake of clarity in the drawings the turnsand number of windings have been limited it will be appreciated that thenumber of windings may be materially increased and the sleevedrelationship of the windings to each other may be as close as thedielectric quality of the insulating material will allow withoutbreakdown.

While power winding of the wire is desirable with all sizes of wire andthe core 6 may be provided in a conventional manner on a shaft drivenfrom the headstock of a lathe as indicated in FIGURE 3, hand winding maybe readily accomplished.

Organic materials useful as the insulation include the resinsparticularly those which soften in heat and resolidify, for example, thestyrenes, methyl methacrylates and vinyl acetates. In general the resinsare utilizable Where the final product is not subjected to excessivetemperature conditions.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions and accordingly,it is desired to comprehend such modifications within this invention asmay fall within the scope of the appended claim.

I claim:

The method of constructing an encapsulated electrical component whichcomprises; winding an electrical conductor wholly within grooves on arigid sleeve-like form of heat softenable electrical insulatingmaterial, placing a second rigid sleeve-like form of heat softenableelectrical insulating material over the first wound form in telescopingrelation, passing the said conductor through passages inwardly of theends of said forms and winding said conductor wholly within grooves onsaid second form to form a continuous winding from said first form tosaid second form, placing a third rigid sleeve-like form of heatsoftenable electrical insulating material over said second form intelescoping relation, said second form being heat softenable at atemperature below the temperature at which the said first and thirdforms will soften, heating the assembled wound forms to at least thesoftening temperature of said second form to fuse the said forms into anintegral mass of electrical insulating material, and thereafter coolingthe sealed component.

812,657 Kitsee Feb. 13, 1906 6 Abbott Oct. 15,

McIntosh Mar. 6,

Majce Dec. 10,

Boyer Mar. 26,

Webb J an. 8,

Dorst May 3,

Whearley May 2,

Tibbetts June 20,

FOREIGN PATENTS Great Britain June 16,

